It's about both..........However having an all powerful Superman eliminates stories like "Panic in the Sky" an episode of the George Reeves TV series, which featured both a physical challenge to Superman and an exploration of his character.
It also features a collaboration between Superman and Earth science to remove the threat. Another facet of the character I prefer....(and I dare say de-powering him is the only way to make it possible) .....that Superman cannot prevent any and all crimes or disaster's both natural and man-made...That he is not looked at as the saviour of Earth by it's populace, but rather a valuable ally, and often it is only that collabortaion that wins the day..

I believe there was some reference to kryptonite being in the asteroid, which is the reason it weakened him enough for the impact to give him amnesia.